Take a kadai or Pan, add oil, when it is hot, add mustard seeds, when it splutters add fennel seeds, curry leaves. Saute for few seconds, when you get Good smell from fennel seeds, add hing & give a quick mix.

Now add marinated potatoes, and simmer the stove at low flame. saute now and then at least for 10 - 12 minutes till it is Roasted.